Air ducts are a major part of heating, ventilating and air-conditioning (HVAC) systems.
Firing may be entirely dispensed with, though care must still be exercised in ventilating.
The Stortz ventilating bronchoscope is the most commonly used rigid bronchoscope in most centers.
This splitting of the air not only lessens the cost of ventilating, but greatly increases its efficiency by permitting the circulation of much larger volumes, and has the added advantage that the effect of an explosion or other accident vitiating the air current is often confined to a single division of the mine, and affects but a small part of the working force.
In devising a system of ventilation it is customary to subdivide the workings so that the resistance to the ventilating current in each split shall be nearly equal, or so that the desired amount of air shall be circulated in each without undue use of regulating appliances which add to the friction and increase the cost of removing the air.
